Fluid operated detector for reciprocating parts



Patented Aug. 11, 1970 INVENTOR M Q M M ATTORNEYS.

United States Patent [72] inventor George Wintriss Carversville, Pennsylvania [21] Appl. No. 697,197 [22] Filed Jan. 11,1968 [45] Patented Aug. 11,1970 [73] Assignee lndustrionics Controls, Inc.

. New York, New York a Corp. of New York [54] FLUID OPERATED DETECTOR FOR RECIPROCATING PARTS 11 Claims, 3 Drawing Figs.

[52] U.S. Cl 91/47, 91/52, 92/99 [51] Int. Cl ..F15b 13/04, F0 1b 19/00, F16j 3/00 [50] Field ot'Search 91/47, 52; 138/45 [56] References Cited UNITED STATES PATENTS 590,892 9/1897 Knight 138/45 2,752,891 7/1956 Farkas 91/47 2,936,788 5/1960 Dahl et a1 138/45 3,087,470 4/1963 Beard et a1.... 91/47 3,401,601 9/1968 Velicer et a1 91/47 FOREIGN PATENTS 1,304,045 10/1962 France 91/47 Primary Examiner- Paul E. Maslousky Attorney- Sandoe, Neill, Schottler and Wikstrom ABSTRACT: This specification discloses apparatus for indicating a failure of a reciprocating part to complete a full stroke. 1f the reciprocating part of a press, molding machine, or other apparatus is prevented from moving to the intended limit of its stroke, through failing to strip a workpiece or from FLUID OPERATED DETECTOR FOR RECIPROCATING PARTS RELATED APPLICATIONS Related patent applications using fluidics for detecting malfunctioning of machines having reciprocating parts are disclosed in my copending applications Ser. No. 484,202, filed Sept. 1, 1965, now abandoned, and Ser. No. 587,547, filed Oct. 18, 1966, now Pat. No. 3,440,374.

BRIEF DESCRIPTION OF THE INVENTION This invention is concerned with apparatus such as presses, molding machines, and the like, where a reciprocating part moves to an intended limit of its stroke when the apparatus is operating satisfactorily. If a work-piece fails to strip and a new blank enters the press over the unstripped piece, or if there is some other obstruction in the mold, the reciprocating part that operates the apparatus cannot move to the intended limit of its stroke, though the straining and elongating of the frame of the apparatus permits the apparatus to continue running and damage is likely to result.

Position sensors are used to determine when parts move together as they should, and to detect a failureto move close enough at the end of a stroke. Since the difference in the stroke for normal operation and malfunctioning amounts to only a few thousandthsof an inch, it is essential'that the parts for detecting malfunction be accurately set with respect to one another.

Sometimes the motion-transmitting connections between a position sensor and the reciprocating part are self-compensating for temperature changes and other influences affecting adjustment, as in my co-pending application Serial No. 512,636; filed December 9, 1965.

This invention is an improvement in malfunction detectors that are not fully self-compensating, and it is an object of the invention to provide an element that moves with a reciprocating part into and out of contact with a sensor with provision for manually bringing the parts into working relation and with automatic provision for adjusting the parts if there is a change of condition that might damage the detector system if not promptly adjusted.

In the preferred embodiment, a fluidic sensor is mounted at a relatively fixed location on the apparatus and this sensor has a fluid passage with a bleed outlet opening through its face. A rod is connected with the reciprocating part by a bracket and moves as a unit with the reciprocating part. A face on one end of the rod confronts the face of the sensor and contacts with the face of the sensor when the reciprocating part is at the intended limit of its stroke, and the coming together of the confronting faces obstructs the flow of fluid from the sensor and produces a pulse in the fluid passage for operating the actuator of an electric switch, valve, or other device for controlling flow of working fluid. 7

It is important, however, that the fluid flow be not fully shut off. While it would seem that a stronger signal could be obtained by a change from a substantial fluid flow to no fluid flow, this being the largest possible percentage of change,

The friction bracket permits the rod to be quickly and conveniently adjusted for the intended position of the reciprocating part before starting the apparatus on its cyclic operation. If the length of the rod changes with temperature so that it contacts with the sensor before the end of the stroke, the friction connection between the bracket and the rod yields as much as necessary to have the parts just touch at the end of the stroke without straining or bending of the rod and resulting in impairment of the operation of the detector. If the rod shortens with temperature change, it can be pushed down manually. Although the fluid passage is preferably in the sensor and the recess in the confronting face of the rod, this is not essential.

, The recess can be in either of the confronting faces, or partly better results are obtained if the flow does not approach zero.

' When the flow is completely blocked, or substantially all blocked, the sensitivity of the sensor is impaired. However, ad-j justment of the parts to have predetermined clearances at the end of a stroke is difficult and unsatisfactory; and this inven tion provides a bracket with friction elements that grip the rod and that yield to permit the rod to be manually pushed into contact with the sensor when the reciprocating part is at the intended limit of its stroke. One of the confronting faces is recessed, as by a channel, above the)oleed outlet so that there is a clearance for the escape of some fluid even when the rod in contact with the sensor ata locatiorrotherth'aathe'recess..

in each, and the fluid passage can be in the rod though it is easier to provide a fluid supply to a stationary sensor.

The invention will be described with an air as the fluid in the sensor, and with an electric switch responsive to changes in the air flow.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIGURE 1 is a fragmentary diagrammatic view of a press equipped with the malfunction detecting apparatus of this invention;

FIGURE 2 is a greatly enlarged fragmentary view, partly in section, of a portion of the structure shown in FIGURE I; and

FIGURE 3 is a sectional view through the sensor shown in FIGURE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGURE 1 shows a press having a frame 10 with a ram 12 that moves up and down in stationary gibs 14 to reciprocate a movable die part 16 toward and from a fixed die part 18. The movable die part 16 is rigidly connected to the ram 12 and the fixed die part 18 is connected to a bed 20 of the press in accordance with conventional practice.

A sensor 22 is attached to a fixed part of the frame 10; and in the drawing is shown attached to one of gibs 14 by fastening means consisting of screws 24. At the upper end of the sensor 22 there is a face 26 which constitutes the top of the sensor housing; and there is an air passage 28 opening through the face 26. The inside construction of the sensor 22 will be described in connection with FIGURE 3. For the present it is sufficient to understand that air, or other gas, is supplied from a pressure line 30through a pressure regulator 32 and supply tubing 34 to the'sensor 22; and that this air-from 'the tubing 34 -1 g A rod 40 is attached to a movable part of the press, and in the construction illustrated, the rod 40 is attached to the ram 12 by a bracket 42 rigidly secured to the ram 12 by screws 44. The rod 40 is held in the bracke't4-2 by friction, and with the rod 40 extending parallel to the direction of travel of the ram 12 and in alignment with the air passage 28. Whe'n the ram 12 1 is at the intended limit of its downward travel; that is, when the die parts 16 and 18 are in their intended closed relationship with one another, the end face at the lower end of the rod 40- contacts with the face 26 of the sensor 22.

FIGURE'Z shows the construction by which the rod 40 is frictionaliy held by the bracket 42-. There are two rings 48 and ifio whic h'flt into counterbores in the bracket 42. These rings may fit with a press fit or may be held in place by fastenings as desired. Whatever construction is used, the rings 48 and 50 are integral with the bracket 42 and the openings in the rings 48 and 50 are slightly larger in diameter than the diameter of the rod 40.

In order to prevent the rod 40 from sliding freely through the rings 48 and 50, there is a flexibly stiff washer 52 located in a recess in the inner face of each of the rings 48 and 50. Each of the washers 52 has an inside diameter smaller than the diameter of the rod 40 so that the washer 52 is distorted when the rod 40 is pushed through the opening in the washer. There is a coil spring 54 in the recess of each of the rings 48 and 50; and these springs 54 are under tension and press the distorted inner edge of each of the washers 52 into friction contact with the cylindrical surface of the rod 40.

The inner edge of each washer 52 serves as a friction brake to prevent movement of the rod 40 axially through the bracket 42. In the preferred construction, one of the washers S2 is distorted upwardly and the other washer 52 is distorted downwardly so that one of them offers its maximum resistance to downward movement of the rod 40 while the other offers maximum resistance to upward movement of the rod 40. However the friction of the washers 52 against the surface of the rod 40 is not sufficient to prevent the rod from moving when given a substantial end thrust by manual force of the operator of the machine.

The springs 54 are merely representative of means for thrusting the washers 52 into friction contact with the rod 40; and the washers 52 with these springs 54 constitute yieldable friction means holding the rod 40 in any set position in the bracket 42. In the operation of the invention, the operator moves the press by hand until the die is fully closed and then pushes the rod 40 downward until the lower end face of the rod is in contact with the face 26 of the sensor 22. There is a channel 60 extending across the lower end face of the rod 40 and this channel 60 is located above the bleed outlet 28. Even when the rod 40 is touching the end face 26 of the sensor, therefor, air can still escape from the bleed outlet 28 by passing through the channel 60 which runs to the side limits of the end face of the rod 40. As previously explained, the channel 60 can be formed in the face 26, or can be formed partly in each of the confronting faces. The essential feature is that when the rod 40 is in its lowermost position, escape of air from the bleed passage 28 must not be completely shut off. it is not clearly understood why this invention works much more satisfactorily when the air flow cannot be shut off completely but experience has shown that the maintaining ofsome flow of air from the bleed passage 28 at all times makes the operation of the sensor more satisfactory and more sensitive to small differences in the stroke of the rod 40. This may be said to be an unexpected result since the complete shutting off of the air would seem to make a larger difference in existing conditions and would seem to be more advantageous for greater sensitivity.

When the press is operating satisfactorily, the rod 40 reciprocates toward and from the face 26 of the sensor and the flow of air from the passage 28 varies from a completely unobstructed flow when the rod 40 is in its raised position to a partially obstructed flow which becomes progressively more obstructed as the end face of the rod 40 approaches the face 26 of the sensor. The minimum flow is reached when the rod 40 touches the face 26 and the actual flow under these conditions depends upon the size of the channel 60 and the pressure of the air discharging from the passage 28.

FIGURE 3 shows the construction of the sensor 22. It includes a housing 158 within which there is a longitudinally extending passage 160 which communicates at its lower end with a chamber 162 having a flexible diaphragm 164 closing the lower end of the chamber 162. A movable contact holder 166 is riveted to the inner lamination of a flexible diaphragm 164. Fixed contacts 168 and 169 are located below the movable contact 166 and are held in place by a ring 170 constructed of insulating material. This ring clamps the circumferential edge region ofthe flexible diaphragm 164.

The fixed electric contacts 168 and 169 are connected with conductors 172 and 174 by helical conductors 176 and 178. The actuator for the switch in the housing 158 is the diaphragm 164 and the air chamber which is closed at its upper end by this diaphragm. The actuator also includes a spring 180 which presses against the movable electric contact and through this contact against the flexible diaphragm 164 in a direction opposite to the pressure exerted by the air in the chamber 162. The switch consists of the movable contact 166, the fixed contacts 168 and 169 and the parts which hold these contacts.

The switch consisting of the contacts 166, 168 and 169 is held open by the spring 180 exerting a force slightly greater than the force of the air pressure in the chamber 162. When the flow of air from the bleed passage 28 is sufficiently obstructed by the rod 40, as previously explained, there is a shock wave in the passage which travels back to the chamber 162 and causes a temporary pressure increase which closes the switch.

The pressure of the spring can be adjusted by means of a screw 182 threaded into the upper end of the guide in which the spring 180 is located. By screwing this screw 182 downwardly, the pressure of the spring 180 against the diaphragm is increased and the air pressure required to close the switch is correspondingly increased. The sensitivity of the switch is increased by having higher pressure of the spring 80 and correspondingly higher air pressure in the chamber 162 and in the passages through which the shock wave travels.

In the construction illustrated, the conductors 172 and 174 connect with a cable 186 which extends through a cap 188 at the bottom of the sensor 22; and this cable 186 leads to the control apparatus for the signal or the automatic stop for the machine.

The tubing 34 is connected with the sensor 22 by a fitting 190 which communicates with an air passage 192 leading into the passage 160. The bleed passage 28 is preferably formed in a bushing 194 that screws into a larger bushing 196 threaded into a counterbore 198 in the top of the housing 158.

The preferred embodiment of the invention has been illustrated and described, and the invention is described in the appended claims.

I claim:

1. Apparatus for detecting the movement ofa reciprocating part to a predetermined limit of its stroke including, in combination, a bumper, means for connecting the bumper with the reciprocating element for movement as a unit therewith, a sensor unit having an end face in the path of movement of the bumper, a fluid passage in the sensor unit with a bleed outlet opening through said end face, another end face on the bumper movable into contact with the end face of the sensor as the bumper completes a reciprocating stroke, the end faces of the bumper and sensor having areas that confront one another, the area of the bumper extending across the bleed outlet and providing an obstruction that covers the bleed outlet when the faces contact with one another, one of the faces having a channel in its confronting area extending to the end of the area of contact with the other face and across the bleed outlet whereby the bleed outlet is not completely blocked when the end faces are in contact with one another, and control means associated with the sensor and responsive to changes in the flow through the bleed outlet.

2. The apparatus described in Claim 1 characterized by the channel being formed in the end face of the bumper and extending entirely across said end face of the bumper.

3. The apparatus described in Claim 1 characterized by the means for connecting the bumper with said reciprocating part being a bracket, the bracket having friction means for holding the bumper in position to contact with the sensor when the reciprocating part is at the intended limit of its stroke.

4. The apparatus described in Claim 3 characterized by the friction means being yieldable and comprising a surface with the bumper can be pushed manually into contact with the end face of the sensor when the reciprocating part is located at the intended limit of its stroke for obtaining an initial setting of the 5. The apparatus described in Claim 4 characterized by the friction means comprising two resilient friction washers located in an opening through the bracket and through which the bumper passes, the resilient washers being spaced from one another axially along the bumper, and each of the resilient washers having its inner edge portion distorted by contact with the bumper, the washers being distorted in opposite directions, and resilient means urging the distorted portions of the washers into contact with a cylindrical surface of the bumper.

6. The apparatus described in Claim 1 characterized by the control means associated with the sensor including an actuator, the sensor having its fluid passage in communication with the actuator, and a device, for sending a signal operated by the actuator in response to pressure pulses in the fluid passage.

7. The apparatus described in Claim 6 characterized by the actuator including a movable wall in contact with fluid from the fluid passage of the sensor, and the device for sending a signal having 'a movable part operably connected with the movable wall and actuated by movement of said movable wall in response to pressure pulses in the actuator.

8. The apparatus described in Claim 7 characterized by the actuator includinga chamber in communication with the fluid passage to the sensor, the movable wall of the actuator being a diaphragm extending across one side of the chamber, and means for supplying fluid under pressure to the chamber including an adjustment device for varying the pressure of the fluid to control the sensitivity of the apparatus.

9. The apparatus described in Claim 8 characterized by the means for supplying fluid and the adjustment for regulating the fluid pressure constituting a pressure regulator with an inlet port for receiving high-pressure fluid, a port through which the fluid passage to the sensor communicates with the chamber of the actuator, means for controlling flow of fluid through the regulator, the actuator being responsive to the fluid pressure on the downstream side of the regulator.

10. Apparatus for detecting the movement of a reciprocating part to a predetermined limit of its stroke including, in combination, two elements that have faces with confronting areas that come together over part of the areas at said predetermined limit, a bracket for connecting one of the elements with the reciprocating element for movement as a unit therewith, the other of said elements being at a fixed location with respect to the reciprocating element, a fluid passage opening through one of the confronting faces and having a bleed outlet that is covered by the other confronting faces when the elements come together, one of the confronting faces having a recessed area open at one side and in position to provide for escape of fluid from the bleed outlet when the elements are in contact with one another.

11. The apparatus described in Claim 10 characterized by the bracket having friction means for holding its connected element in position to contact with the other element when the reciprocating part is at the intended limit of its stroke, said friction means being yieldable and comprising a surface with resilient means holding it in contact with the other element at the end of a stroke whereby the element that moves with the reciprocating part can be pushed manually into contact with said end face of the other element when the reciprocating part is located at the intended limit of its stroke for obtaining an initial setting of the first element in the bracket before starting a cyclic operation of the reciprocating part. 

